US20220056635A1

US20220056635A1 - Coated Antimicrobial Fabric

Info

Publication number: US20220056635A1
Application number: US17/399,115
Authority: US
Inventors: Geoffrey M. Baldwin
Original assignee: Specialty Coating and Laminating LLC
Current assignee: Specialty Coating and Laminating LLC
Priority date: 2020-08-20
Filing date: 2021-08-11
Publication date: 2022-02-24
Also published as: US20220056636A1

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,” 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.

Description

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.
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

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.
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

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.
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 20-120 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 coextruded onto the nonwoven fabric substrate with the coextruded coating comprising a plurality of layers and only one of the layers includes the antimicrobial material. The coated nonwoven fabric may have a permeability rating of 5-70 Perms. The antimicrobial material coating may alternatively be an aqueous solution applied to the nonwoven substrate and then dried onto the substrate.
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 coextruded onto the nonwoven fabric substrate with the coextruded coating comprising a plurality of layers and only one of the layers includes the antimicrobial material. The coated nonwoven fabric may have a permeability rating of 0 to less than 5 Perms.
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 coextruded onto the fabric substrate with the coextruded 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

FIG. 1 is a schematic drawing of a coating process in accordance with the invention described herein.

FIG. 2 is a schematic of a complete extrusion coating process as described in an example of the present invention.

FIG. 3 is a schematic of an aqueous coating process that may be used in connection with an example of a process described herein.

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.

FIG. 5 is a schematic drawing of a coextrusion coating process in accordance with the invention described herein.

DETAILED DESCRIPTION

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.
Intended uses for this fabric include, but are not limited to, as a wearable garment, hair coverings, “booties,” temporary curtains, instrument wraps, surgical drapes, and blankets.
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.
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.
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.
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 CaCO₃, titanium dioxide TiO₂, and calcium hydroxide Ca(OH)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.
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.
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.
In addition to being a single layer extrusion coating as described above, it is possible to use a coextruder 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 coextruded 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 solely a polymer or copolymer material.
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.
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 US Perms, defined as transmitting 1 grain of water vapor/hour/sq. ft. @ 1″ mercury pressure. 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 WTVR or Perm rate. The current coated nonwoven material described herein after activation has a US Perm rate of 5-70 Perms, or 10-30 Perms.
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 US Penn rate of 0 to less than 5.
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.
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® 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/m²wet 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.
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 50% CaCO₃and 1% TiO₂by weight demonstrates an ability to kill 22% of staphylococcus aureus bacterial cultures within 24 hours by the AATCC 100 test method. 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.
Another class of antimicrobial and antiviral additives includes compounds containing silver or copper. These additives include silver-containing coatings available from Techmer and others. 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.
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.
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.
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.
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 coextrusion of two layers of polymer.
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.
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.
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. The now-dry web 116 is cooled by roller 114 and wound up into a roll 118.
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.
In FIG. 5, the 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 a pair of extrusion melt streams 162 and 164 that contain the appropriate additives that are extruded into the nip between the nip roller 156 and chill roll 168 that hardens the polymers 162 and 164 onto the surface of the web 152. Specifically, as discussed earlier herein, the extrusion polymer 162 from die 158 will be the outside or top layer of the finished coated web 172. As such, the polymer of extrusion melt 162 will contain the antimicrobial components and will be a relatively thin or skin layer. The extrusion melt 164 extruded by die 160 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 coextruded polymer layers 174 and 176.
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

An antimicrobial two-layer, nonwoven base fabric is coated with a microporous coating. This particular example has the following specifications:
Weight—72 gsm (TAPPI T410)
Thickness—14 mil (TAPPI T411)
Base Material—40 gsm
Coating Material—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:
Antiviral Effectiveness (Human Coronavirus OC43)—98% (ISO 18184)
Antibacterial Effectiveness (MRSA & Staph)—99.99% (AATCC 100)
Liquid Resistance—20 in+ (AATCC 127)
It is readily apparent from the foregoing that the fabric described herein is an effective antimicrobial and antiviral barrier.
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.

Claims

That which is claimed is:

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 20-120 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 coextruded onto the nonwoven fabric substrate with the coextruded 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 permeability rating of 5-70 Perms.

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,

13. An antimicrobial fabric as described in claim 11,

14. An antimicrobial fabric as described in claim 11,

wherein the coated nonwoven fabric has a permeability rating of 0 to less than 5 Perms.

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,

18. An antimicrobial fabric as described in claim 15,

wherein the antimicrobial coating is coextruded onto the fabric substrate with the coextruded 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.