U.S. patent application number 17/406551 was filed with the patent office on 2022-02-24 for coated antimicrobial fabric.
This patent application is currently assigned to Specialty Coating & Laminating, LLC. The applicant listed for this patent is Specialty Coating & Laminating, LLC. Invention is credited to Geoffrey M. Baldwin.
Application Number | 20220056636 17/406551 |
Document ID | / |
Family ID | |
Filed Date | 2022-02-24 |
United States Patent
Application |
20220056636 |
Kind Code |
A1 |
Baldwin; Geoffrey M. |
February 24, 2022 |
Coated Antimicrobial Fabric
Abstract
A nonwoven fabric has active antimicrobial and anti-viral agents
coated onto it. Alternatively, an active antimicrobial/antiviral
agent may be mixed into the barrier coating or fiber polymers
themselves that make up the nonwoven material. A primary example is
the treatment of an existing fabric having known permeability
appropriate for an intended use. Intended uses for this nonwoven
fabric include, but are not limited to, as a wearable garment, hair
coverings, "booties," patient cubicle curtains, temporary curtains,
instrument wraps, surgical drapes, and blankets, each of which has
active antimicrobial protection, thereby allowing the possibility
of multiple uses of the fabric product.
Inventors: |
Baldwin; Geoffrey M.;
(Mechanicsville, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Specialty Coating & Laminating, LLC |
Doswell |
VA |
US |
|
|
Assignee: |
Specialty Coating & Laminating,
LLC
Doswell
VA
|
Appl. No.: |
17/406551 |
Filed: |
August 19, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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63067987 |
Aug 20, 2020 |
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International
Class: |
D06M 11/84 20060101
D06M011/84; D06M 11/44 20060101 D06M011/44; D06M 11/46 20060101
D06M011/46; D06M 11/76 20060101 D06M011/76 |
Claims
1. An antimicrobial fabric comprising: a nonwoven fabric substrate
formed of spunbonded polymer fibers; an antimicrobial material
coated onto the nonwoven fabric substrate; wherein the coated
nonwoven fabric is permeable to vapor and substantially impermeable
to liquids.
2. An antimicrobial fabric as described in claim 1, wherein the
fabric is coated on both sides by an antimicrobial material.
3. An antimicrobial fabric as described in claim 1, wherein the
polymer fibers that form the nonwoven fabric substrate are
polyolefin fibers.
4. An antimicrobial fabric as described in claim 1, wherein the
uncoated nonwoven fabric substrate has a base weight of 20-200
g/m2.
5. An antimicrobial fabric as described in claim 1, wherein the
uncoated nonwoven fabric substrate has a thickness of 0.0025-0.030
inches.
6. An antimicrobial fabric as described in claim 1, wherein the
antimicrobial material is comprised of one or more compounds
selected from the group consisting of CaCO3, TiO2, and Ca(OH)2.
7. An antimicrobial fabric as described in claim 1, wherein the
coated fabric is stretched after extrusion.
8. An antimicrobial fabric as described in claim 1, wherein the
antimicrobial coating is co-extruded onto the nonwoven fabric
substrate with the co-extruded coating comprising a plurality of
layers and only one of the layers includes the antimicrobial
material.
9. An antimicrobial fabric as described in claim 1, wherein the
coated nonwoven fabric has a WVTR of 35-4900 g/m2/24 hrs.
10. An antimicrobial fabric as described in claim 1, wherein
antimicrobial material coating is an aqueous solution applied to
the nonwoven substrate and then dried onto the substrate.
11. An antimicrobial fabric comprising: a nonwoven fabric substrate
formed of spunbonded polymer fibers; an antimicrobial material
coated onto the nonwoven fabric substrate; wherein the coated
nonwoven fabric is substantially impermeable to vapor and
substantially impermeable to liquids.
12. An antimicrobial fabric as described in claim 11, wherein the
antimicrobial material is comprised of one or more compounds
selected from the group consisting of CaCO3, TiO2, and Ca(OH)2.
13. An antimicrobial fabric as described in claim 11, wherein the
antimicrobial coating is co-extruded onto the nonwoven fabric
substrate with the co-extruded coating comprising a plurality of
layers and only one of the layers includes the antimicrobial
material.
14. An antimicrobial fabric as described in claim 11, wherein the
coated nonwoven fabric has a WVTR of 0 to less than 35 g/m2/24
hrs.
15. An antimicrobial fabric comprising: a fabric substrate; an
antimicrobial material coated onto the fabric substrate; wherein
the coated fabric is permeable to vapor and substantially
impermeable to liquids.
16. An antimicrobial fabric as described in claim 15, wherein the
fabric substrate is a woven or knitted material.
17. An antimicrobial fabric as described in claim 15, wherein the
antimicrobial material is comprised of one or more compounds
selected from the group consisting of CaCO3, TiO2, and Ca(OH)2.
18. An antimicrobial fabric as described in claim 15, wherein the
antimicrobial coating is coextruded onto the fabric substrate with
the co-extruded coating comprising a plurality of layers and only
one of the layers includes the antimicrobial material.
19. An antimicrobial fabric as described in claim 15, wherein the
fabric is coated on both sides by an antimicrobial material.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application 63/067,987 filed on Aug. 20, 2020, which is
incorporated by reference herein in its entirety.
[0002] The field of the invention is breathable and non-breathable
coatings applied to, for example, a nonwoven, woven, or knitted
fabric that has active antibacterial and/or antiviral properties
added through a variety of technologies. The fabric may be used in
the manufacture of personal protective garments, for instance, and
other personal protective equipment (PPE) and also used in the
healthcare industry generally, for instance as patient privacy
curtains.
BACKGROUND
[0003] Fabrics that are both liquid barriers but also vapor
permeable are used widely in the healthcare field. Traditionally,
these garments and drapes are used for one-time duty and may be
disposed thereafter. The conventional wisdom for this use in the
healthcare field, for instance, is that the fabrics are a barrier
to patient blood and other bodily fluids that may carry infections
or other disease. These fabrics are available in both vapor barrier
and non-vapor barrier materials. It can be desirable to have
fabrics that are breathable so that the garments are comfortable
for use.
[0004] A nonwoven fabric alone, in one example, provides little to
no resistance to penetration by liquids. Coating the surface of the
fabric with a thin layer of solid polymer provides such protection
but can also trap moisture and heat when fashioned as a wearable
garment.
SUMMARY
[0005] Accordingly, it is an object of the present invention to
overcome the existing drawbacks in the healthcare industry
especially by providing a coated antimicrobial fabric. This fabric
is both a barrier to air and liquids, but it is at the same time
breathable. Additionally, the fabric blocks and actively kills
microbes that might penetrate or try to penetrate the fabric.
[0006] In one example, an antimicrobial fabric comprises a nonwoven
fabric substrate formed of spunbonded polymer fibers and an
antimicrobial material coated onto the nonwoven fabric substrate.
The coated nonwoven fabric is permeable to vapor and substantially
impermeable to liquids. The fabric may be coated on both sides by
an antimicrobial material. The polymer fibers that form the
nonwoven fabric substrate may be polyolefin fibers. The uncoated
nonwoven fabric substrate may have a base weight of 20-200 g/m2.
The uncoated nonwoven fabric substrate may have a thickness of
0.0025-0.030 inches. The antimicrobial material may be comprised of
one or more compounds selected from the group consisting of CaCO3,
TiO2, and Ca(OH)2. The coated fabric may be stretched after
extrusion. The antimicrobial coating may be co-extruded onto the
nonwoven fabric substrate with the co-extruded coating comprising a
plurality of layers and only one of the layers includes the
antimicrobial material. The coated nonwoven fabric may have a WVTR
permeability of 35-4900 g/m2/24 hrs. The antimicrobial material
coating may alternatively be an aqueous solution applied to the
nonwoven substrate and then dried onto the substrate.
[0007] In another example, an antimicrobial fabric comprises a
nonwoven fabric substrate formed of spunbonded polymer fibers and
an antimicrobial material coated onto the nonwoven fabric
substrate. The coated nonwoven fabric is substantially impermeable
to vapor and substantially impermeable to liquids. The
antimicrobial/antiviral material may be comprised of one or more
compounds selected from the group consisting of CaCO3, TiO2, and
Ca(OH)2. The antimicrobial coating may be co-extruded onto the
nonwoven fabric substrate with the co-extruded coating comprising a
plurality of layers and only one of the layers includes the
antimicrobial material. The coated nonwoven fabric may have a WVTR
permeability of 0 to less than 35 g/m2/24 hrs.
[0008] In a still further example, an antimicrobial fabric
comprises a fabric substrate and an antimicrobial material coated
onto the fabric substrate. The coated fabric is permeable to vapor
and substantially impermeable to liquids. The fabric substrate may
be a woven or knitted material. The antimicrobial material may be
comprised of one or more compounds selected from the group
consisting of CaCO3, TiO2, and Ca(OH)2. The antimicrobial coating
may be co-extruded onto the fabric substrate with the co-extruded
coating comprising a plurality of layers and only one of the layers
includes the antimicrobial material. The fabric may be coated on
both sides by an antimicrobial material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic drawing of a coating process in
accordance with the invention described herein.
[0010] FIG. 2 is a schematic of a complete extrusion coating
process as described in an example of the present invention.
[0011] FIG. 3 is a schematic of an aqueous coating process that may
be used in connection with an example of a process described
herein.
[0012] FIG. 4 is a schematic drawing of a coating process in
accordance with the invention described herein where the fabric is
coated on both sides.
[0013] FIG. 5 is a schematic drawing of a co-extrusion coating
process in accordance with the invention described herein.
DETAILED DESCRIPTION
[0014] The present invention is directed to a fabric that has
active antimicrobial and/or anti-viral agents coated onto it.
Alternatively, an antimicrobial/antiviral agent may be mixed into
the barrier coating or fiber polymers themselves that make up the
fabric material. A primary example is the treatment of an existing
fabric having known permeability appropriate for an intended
use.
[0015] Intended uses for this fabric include, but are not limited
to, as a wearable garment, hair coverings, "booties," patient
cubicle curtains, temporary curtains, instrument wraps, surgical
drapes, and blankets.
[0016] Throughout this description, the terms antimicrobial,
antibacterial, antifungal and antiviral are often all or partially
referred to together. For the purposes of the present invention,
the term antimicrobial is inclusive of and refers to all of
antiviral, antibacterial and antifungal.
[0017] The base fabrics discussed herein are mostly nonwoven
fabrics. However, other fabrics including conventional woven and
knitted textile fabric products may also be coated as described
herein. Moreover, even extruded or cast film fabrics may likewise
be coated as described herein. The coating processes are similar if
not exactly the same as described. In each base fabric example, the
resulting coated fabric may be substantially impermeable to liquid
and gas, or it may be permeable to liquid and/or water vapor and
other small molecular diffusion.
[0018] The example of a nonwoven base fabric is a substrate of
nonwoven spunbonded polymer fibers. The fibers that may be used
include polyethylene, polypropylene, polyester, nylon, polyvinyl
chloride, bicomponent fibers and mixtures of two or more of the
foregoing. In one example of the present fabric, the base fabric
has a weight of 20-120 g/m2 (also referred to as gsm), or 30-70
g/m2, or in one example, about 40 g/m2. The thickness of the base
fabric before further processing is 0.0025-0.030 inches, or
0.003-0.020 inches, or still further 0.005-0.012 inches. This
thickness is the lofted thickness of the nonwoven fabric before
extruding any coating thereon.
[0019] Next, the nonwoven base fabric has a coating applied to it
by extrusion coating. This coating may be applied on one or both
sides of a base fabric. For a breathable fabric that is impermeable
to water but permeable to water vapor, incorporating an appropriate
level of finely ground mineral into the polymer coating, and then
stretching the fabric to create microscopic fractures in the
coating provides a path for small molecular diffusion while
preserving liquid holdout. Certain types of ground mineral such as,
but not limited to, calcium carbonate CaCO.sub.3, titanium dioxide
TiO.sub.2, and calcium hydroxide Ca(OH).sub.2, for instance, have
known antimicrobial/antiviral properties in that the rough peaks of
the ground mineral tend to pierce and destroy the outer protective
envelope of certain microorganisms.
[0020] The molten polymer coating material is extruded and combined
by nip where one roller makes contact to the base fabric (uncoated
side) which is then quenched by nipping it against a chilled roller
to bond the coating onto the fabric. The heated coating material
allows the intertwining of the molten polymer material into the
nonwoven fabric. Importantly, this means that no adhesive is
required to attach the coating layer onto the nonwoven base fabric.
Therefore, there is no concern about future degradation of an
adhesive. Alternatively, a film could be produced and adhesively
laminated as well. The film could also be made without the ground
minerals. If desiring a fabric with both sides coated, then a
starting base fabric coated on one side is inserted in the above
process only the new extrusion coating is applied to the opposite
side of the base fabric to result in a two-sided coated fabric.
[0021] The coating can be a base resin with the
antibacterial/antiviral additives added or for a breathable coating
a mixture of polymer and inorganic particles such as calcium
carbonate, or both antimicrobial additive and small particles, can
also be added. The polymer portion of the coating is typically
polyethylene or polypropylene, but it could include other polymers
as well. If polyethylene, then the density of the polyethylene is
0.908-0.925, or alternatively, 0.918-0.923 grams per cubic
centimeter (g/cm3). If polypropylene, then the density is 0.89-0.92
g/cm3, or alternatively, 0.90-0.91 g/cm3. In the example of calcium
carbonate, the ground mineral is 35-75% by weight of the coating
mixture, or alternatively 40-60% by weight. In the example of
calcium hydroxide (Ca(OH)2), the ground mineral is 1-65% by weight
of the coating mixture, or alternatively 5-30% by weight, or
further alternatively about 10-20% by weight. Additional additives
in the coating mixture include pigment, UV inhibitors, and
processing aids. Importantly, there is no adhesive fraction in the
coating mixture. The coating weight of the coating mixture on the
base fabric is 20-55 g/m2, or alternatively, 30-40 g/m2.
[0022] In addition to being a single layer extrusion coating as
described above, it is possible to use a co-extruder tool to coat a
two or more layer polymer onto the same side of a base web of
nonwoven fabric. In one example of a co-extruded polymer layer, the
polymer layer may have a thin top layer (skin layer) that is
heavily mixed with a ground mineral and antibacterial and antiviral
additives, while the majority of the polymer layer is a polymer or
copolymer material.
[0023] The coated nonwoven fabric may be used as is in the form of
a substantially impermeable coated fabric. In the example of a
permeable fabric, that coated fabric is next activated by
stretching in order to create micropores across and through the
coating layer. The coated fabric may be activated by stretching
with or without heat added to the coated fabric. The stretch may be
in the machine direction or cross direction or a combination of
both directions. In one example, intermeshing gears are used to
stretch the fabric in the cross-direction in non-uniform fashion.
This may result in the stretching in the cross-direction of about
40% or less, or alternatively about 20% or less, or still further
alternatively about 1-10%. The result is a breathable sheet that is
substantially impermeable to liquid water yet permeable to gas/air
that flows through the pores around the calcium carbonate in the
polymer layer.
[0024] Permeability is measured and rated by many methods and units
for films and fabrics. In the US, the ASTM E96 methods are often
used, and those results can be expressed in units of g/m2/24 hrs
(WVTR). The test method employs a sealed cup containing a desiccant
material, covered by the fabric under test, which is placed into a
chamber having a controlled temperature and humidity (usually 100
deg F. and 90% RH). The weight gain of the desiccant is monitored
over time until a steady-state is reached, and the steady state is
reported as the WVTR. The current coated nonwoven material
described herein after activation has a WVTR of 35-4900 g/m2/24
hrs. or 70-2100 g/m2/24 hrs.
[0025] While many embodiments of the fabric and resulting garments
described herein have some breathability for the comfort of the
wearer, an alternative of the fabric and garments described herein
is a coated fabric that is substantially impermeable to water and
water vapor. In these examples, there would be no activation of the
coated fabric as described above. The result is a coated fabric
that is substantially impermeable, defined herein as having a WTVR
of 0 to less than 35.
[0026] Liquid holdout (hydrostatic head) properties of a fabric,
which can potentially be compromised by the activation process
described earlier herein, is measured and rated by the AATCC 42 and
AATCC 127 test methods. AATCC 42 measures resistance to water
impact, as a stream of water falls onto a swatch of fabric held at
a 45 degree angle to the vertical, backed by a piece of blotter
paper. The weight gain of the blotter paper is measured after an
appropriate test period and flowrate. AATCC 127 measures the water
pressure at which the fabric is made to leak, as a layer of fabric
is clamped into a sealed fixture while a column of water is filled
above to a measured height, while watching for the first drops to
penetrate. The relative protective level of isolation clothing is
specified within the AAMI PB70 standard with a rating from Level 1
(minimally protective) to Level 4 (very protective). The coated
fabric described herein may have a Level 1 to 4 depending on the
intended use of the fabric and type of fabric and coating, or
alternatively, a level of 2-3. In one example, a coated fabric for
use as a garment has been tested and is capable of providing a
Level 3 protection by admitting no more than 0.1 grams of water in
the AATCC 42 water impact test and surviving a minimum pressure of
20'' of water head without leakage as defined testing under the
AATCC 127 hydrostatic head test.
[0027] Active antimicrobial and antiviral features may
alternatively or additionally be incorporated to the coated fabric
by the application of a sanitizing coating applied to the surface
of the material, such as quaternary alkyl dimethyl benzyl ammonium
chloride dihydrate. This quaternary benzyl ammonium chloride is a
disinfecting agent often used in cleaning products within the food
industry to attack and destroy microorganisms. Alternative
disinfecting agents include isopropyl alcohol, ethanol, larger
alcohols, citric acid, and secondary alcohol ethoxylates. These and
other disinfectants include those sold, for instance, under the
Microban.RTM. trademark in the extrudate or as an after coating
over the extrudate. Such chemicals attack and dissolve proteins and
lipids in the outer protective envelope of an organism, thwarting
the pathogen's mode of infection. When an aqueous solution of the
above chemical with a concentration of 800 ppm is applied to the
surface of the fabric at a rate of 2.5 g/m.sup.2 wet and then dried
at 200 deg F., the resulting dried fabric surface is demonstrated
to kill 96% of Staphylococcus aureus and 93% of MRSA bacterial
cultures within 24 hours by the AATCC 100 test method. AATCC 100
involves the preparation and application of selected bacterial
cultures to the surface of a test fabric alongside that of a
control fabric, while the rate of growth or lack thereof is
monitored and compared visually over the test period.
[0028] Alternatively, such active antimicrobial and antiviral
performance properties can come from contact with the ground
mineral particles incorporated into the polymer barrier coating
itself. Calcium carbonate, titanium dioxide, and calcium hydroxide
are expected to disable and kill microbes by disrupting and
piercing the protective outer layer of some varieties. A coating
containing approximately 25% Ca(OH)2, 25% CaCO.sub.3 and 1%
TiO.sub.2 by weight demonstrates an ability to kill human
coronavirus OC43 at 98% (ISO 18184). The antimicrobial/antiviral
must be able to kill germs or viruses or bacteria or at least
reduce or eliminate dwell time of such microbes when they are
captured in the fabric.
[0029] Other classes of antimicrobial and antiviral additives
include compounds containing silver or copper. These additives
include silver-containing coatings available from Techmer and
others. These additives in addition to the minerals above were
effective against MRSA and staph at 99.99% (AATCC-100). This
additive is applied at a 2% by weight of a coating, or
alternatively 1-3%, or further alternatively 0.5-5% by weight.
Additional silver and/or copper containing additives are
available.
[0030] Importantly, the antimicrobial and antiviral additive must
not materially reduce the fluid impermeability and vapor
permeability performance characteristics of the fabric, in the
example of a permeable coated fabric. At the very least, a coating
must reduce those characteristics an acceptable amount.
Qualitatively speaking, the liquid coating must be very thin, and
the particle coating must include small particles.
[0031] Another important aspect in the selection of an active
antimicrobial and antiviral is the toxicity of that antimicrobial
and antiviral to a human user of the fabric. The aqueous coating
used in the above example is a well-known very safe disinfecting
agent, approved for food contact under US EPA article 40 CFR
180.940. In other examples, the coating is oriented away from the
human body by design of the protective garment (for instance, a
single-coated fabric has the coated side on the outside of the
garment away from the user's skin). Also, by carefully selecting
the coating products, a fabric coated on both sides may be used to
mitigate blood borne pathogens.
[0032] The coated fabrics may be widely used for purposes of
isolation from microbial hazards. The sheets of fabric may be used
to make the garments and drapes (coated both sides). The fabric
sheets may be cut and sonically welded, or heat sealed or sewn to
form a garment. In this example, the antimicrobial and antiviral
must be chosen so that it does not reduce the ability of that
fabric web to be sonic welded or heat sealed. The very thin
antimicrobial coating does not interfere with downstream
processing, nor does the internal mineral content of the coatings
diminish the heat seal properties of the fabric alone or an already
extrusion coated nonwoven base web. Importantly, the figures
illustrate a base web of a nonwoven fabric material. It is equally
possible that the base fabric is a textile woven or knitted
material or an extruded or cast film fabric. The drawings would be
exactly the same but for the composition of the base fabric, so
additional drawings are not necessary to show each of these
examples of alternative base web materials.
[0033] The attached FIGS. 1-5 illustrate examples of alternative
methods of applying a coating onto the nonwoven base fabric. FIG. 1
shows the extrusion coating of a molten polymer that is nipped and
chilled to secure the coating onto and into the nonwoven fabric.
FIG. 2 illustrates a similar coating process, except that the
fabric is then stretched between activator rolls (intermeshing
gears) as described earlier. FIG. 3 illustrates a coating process
where the coating is an aqueous solution that is heated to remove
the water to leave the coating on the nonwoven base fabric. FIG. 4
illustrates the extrusion coating of a molten polymer that is
nipped and chilled to secure a coating on a base fabric that is
already coated on its opposite side in an earlier pass. And
finally, FIG. 5 is similar to FIG. 1 except that the coating that
is applied to the nonwoven base fabric is a co-extrusion of two
layers of polymer.
[0034] In FIG. 1, the extrusion coating system 10 begins with the
input of a non-woven fabric web 12 formed of a flat web of nonwoven
fibers 14. The web is then guided by nip roller 16 and pressed into
a mixed extrusion melt 20 that contains the appropriate additives
that is extruded into the nip between the nip roller 16 and chill
roller 22 to chill and harden the polymer 20 onto the surface of
the web 12. The polymer of the extrusion melt 20 is heated and
extruded onto the web 12 by a die 18. The strip roll 24 pulls the
coated web 26 off of the chill roll 22. The coated web 26 is formed
of a non-woven fabric 12 formed of fibers 14 coated on one side
with the polymer layer 28.
[0035] FIG. 2 illustrates a coating system 50 that also includes an
activation step. The process begins with a roll 52 of non-woven
fabric 52. The non-woven fabric 54 is unwound and passes around a
nip roll 56 next to a chill roll 66. A hopper 58 contains a polymer
resin that is heated and extruded in an extruder 60 into a die 62
which deposits a layer of polymer 64 onto the non-woven fabric 54
between the nip roll 56 and the chill roll 66. When in contact with
the chill roll 66, the polymer layer 64 solidifies and is bonded
into the non-woven fabric 54. This coated web is then edge trimmed
in a slitter 70 and then guided by spreader rollers 72 through the
activator 74 to achieve the coated and activated fabric 76 that is
then wound onto roll 78.
[0036] FIG. 3 illustrates an aqueous coating system 100 that is an
alternative to or in addition to the melt coating systems 10 and 50
in FIGS. 1 and 2. In the aqueous coating system 100, a roll of
non-woven web is unrolled to a single sheet of non-woven web 104
that then passes between rollers 108. The web 108 may be a plain
nonwoven polymer web, or it may be a previously coated nonwoven
web. The bottom roller of rollers 108 picks up an aqueous coating
from a bath 106 and applies it onto the nonwoven web 104. The
rollers 108 then press the aqueous fluid from bath 106 and press it
into the non-woven fabric 104 to form a saturated web 110. This web
110 then passes through an oven 112 that dries the water out of the
aqueous coating and can be aided in drying by the use of a heated
roll 113 or rollers. The now-dry web 116 is cooled by roller 114
and wound up into a roll 118.
[0037] In FIG. 4, the extrusion coating system 120 begins with the
input of a non-woven fabric web 122 formed of a flat web of
nonwoven fibers 124 already coated with a polymer coating 126 as
described herein on one side of the web. The single-side, coated
web 122 is then guided by nip roller 128 and pressed into a mixed
extrusion melt 132 that contains the appropriate additives that is
extruded into the nip between the nip roller 128 and chill roller
134 to chill and harden the polymer 132 onto the surface of the web
122. The polymer of the extrusion melt 132 is heated and fed onto
the web 122 by a die 130. The strip roll 136 pulls the coated web
138 off of the chill roll 134. The coated web 138 is formed of a
non-woven fabric 138 formed of fibers 124 coated on one side with
the polymer layer 126 and the opposite side with a second polymer
layer 140.
[0038] In FIG. 5, the co-extrusion coating system 150 begins with
the input of a nonwoven fabric web 152 formed of a flat web of
nonwoven fibers 154. The web is then guided by nip roller 156 and
pressed into the co-extrusion melt stream 162 that contains the
appropriate additives that are extruded into the nip between the
nip roller 156 and chill roll 168 that hardens the polymers in
extrusion melt stream 162 onto the surface of the web 152.
Extruders A and B, items 160 and 161 respectively, feed into a
feedblock 159 to take the two molten polymer extrudates A and B and
combine them into a single extrudate 162 with an A/B structure. The
extrudate 162 comes out of the single die 158 and is nipped and
chilled as in the monolayer process described earlier.
Specifically, the extrusion polymers 162 from die 158 will be the
outside or top layer of the finished coated web 172. As such, the A
polymer of extrusion melt 162 will contain the antimicrobial
components and will be a relatively thin or skin layer. The B
polymer of extrusion melt 162 extruded by die 158 will be
exclusively or near exclusively a polymer as described earlier
herein. The strip roll 170 pulls the coated web 172 off of the
chill roll 168. The coated web 172 is formed of a nonwoven base
fabric 152 formed of fibers 154 coated on one side with the
co-extruded polymer layers 174 and 176.
[0039] In one example, the co-extruded coating is a two-layer, also
known as A/B, coating. Typically, but not always, one of the A/B
layers is relatively thin as compared with the other layer. In the
FIG. 5 example, the coated web has a coating of about 50% each of
polymer layers 174 and 176. It is likely that one layer, for
instance containing the antimicrobial and ground mineral particles
may be 5-65%, or alternatively 10-40% or 20-30%, of the co-extruded
polymer with the balance being the simple base polymer as discussed
earlier herein.
[0040] FIG. 5 shows a two-layer A/B co-extrusion. It is also
possible to have three or more layers of a co-extrudate. For
example, these may be A/B/A or B/A/B or A/B/C in structure. These
three or more layers of coextrusion would be fed into a die through
a feedblock as shown in FIG. 5 with two or more extruders, or three
or more extruders if three or more polymer layers are intended. An
A/B/A co-extrudate, for instance, could have only two extruders as
shown in FIG. 5 but with a die that feeds out an A/B/A
co-extrudate.
[0041] Any of these coating systems may be used to achieve the
present invention. Moreover, variations to the foregoing systems
and different types of systems altogether may be used.
Example
[0042] An antimicrobial two-layer, nonwoven base fabric is coated
with a microporous coating. This particular example has the
following specifications:
[0043] Weight--72 gsm (TAPPI T410)
[0044] Thickness--14 mil (TAPPI T411)
[0045] Base Material--40 gsm
[0046] Coating Material (25% Ca(OH)2, 25% CaCO2, 2%
antimicrobial)--35 gsm
This fabric was manufactured as described in FIG. 2 and
accompanying description. The coated fabric was tested for barrier
and antimicrobial performance with the following results:
[0047] Antiviral Effectiveness (Human Coronavirus OC43)--98% (ISO
18184)
[0048] Antibacterial Effectiveness (MRSA & Staph)--99.99%
(AATCC 100)
[0049] Liquid Resistance--20in+ (AATCC 127)
[0050] It is readily apparent from the foregoing that the fabric
described herein is an effective antimicrobial and antiviral
barrier.
[0051] Other embodiments of the present invention will be apparent
to those skilled in the art from consideration of the
specification. It is intended that the specification and figures be
considered as exemplary only, with a true scope and spirit of the
invention being indicated by the following claims.
* * * * *